Apparatus and techniques for the faithful reproduction of sound have been the subject of a great deal of development effort. The benefits of high-quality sound reproduction include increased listening pleasure of musical compositions and multimedia presentations, movies, television shows and the like. More realistic sound reproduction is also desirable in order to provide increased intelligibility of oral communications under difficult circumstances, e.g., for public speakers located in extremely noisy environments.
Despite many attempts throughout the years and various advances in both analog and digital audio technology, complete audio accuracy has still not been achieved with existing sound reproduction systems. Audiophiles and others are continually striving to achieve sound reproduction which, in effect, places the listener in the audience. This goal has been elusive, although many improvements have been made in recent years that are providing listeners with more realistic audio experiences. In spite of recent advancements, there is still room for improvement.
One known stereophonic system attempts to produce electrical signals which faithfully represent what a person actually located in the sound field of interest would hear by utilizing microphones positioned to duplicate the human ears. In some instances, the microphones have been actually placed on or encased in a mannequin or model of a head in an attempt to capture the sound as it is actually heard by a physically present listener, influenced by head and ear size, bone construction, and other factors. If the signal recorded by such a system is reproduced in a quality stereo apparatus and presented to the listener by means of a stereophonic headset, a marked improvement in directionality is observed. In particular, the listener's ability to determine the relative location of each particular sound source contributing to the overall recorded sound field is enhanced. This improvement in directionality, in turn, imparts the sensation of greater realism. For example, where the reproduced sound is musical entertainment, the listener's sense of impression as to the localization of each musical instrument and each voice is greatly improved. When the reproduced sound is speech in which there is either a high background noise level or several speakers engaging in rapid conversational exchange, the listener's ability to ascertain what is said by a speaker is significantly enhanced. Although this prior art system has demonstrated improved directionality and realism, it has not achieved that degree of improvement over more conventional recording and reproduction systems required to create widespread interest and application.
Another prior art system, described in U.S. Pat. No. 3,985,960 to Wallace, Jr. provides a binaural sound recording and reproduction system that utilizes a recording mannequin (dummy) equipped with an electroacoustic model of the human auditory tract to record the sound pressure that would be exerted on a listener's eardrum. This system also utilizes a headset with in-ear transducers or receivers that exhibit a flat frequency response as measured at the listener's eardrums. The receiver units utilize acoustic impedance matching to the listener's ear canal to effect a flat frequency response characteristic. An equalizer circuit is provided to facilitate the use of the in-ear receivers with conventionally recorded sound.
The primary purpose of these recording technologies, from binaural to multi-channel is to try to engineer recordings to simulate the original environment when the recordings are played back, e.g., through headphones. There are also headphone systems that attempt to recreate a live environment, similar to the way multi-channel surround systems do for speakers. In all of these systems known to date, there are nagging differences between what the human listener actually hears and what a “proxy device” can attempt to recreate through technology. To date, there has been no connection between how something is recorded and how the recording is played back by the user.
It would be advantageous to tie together the recording technology or technologies used to make a recording with the playback mechanisms used by the listener. It would be particularly advantageous to eliminate as many variables as possible that exist in the various choices in playback devices (e.g., mp3 players, smart phones, computers, tablets, etc.) used by the listener as well as the headphones used to reproduce the audio content. It would be still further advantageous to provide one or more databases of recording technologies (e.g., microphones, recorders, etc.) and their effect upon the original acoustic environment in which audio content is created, the playback mechanism chosen by the user and its potential changes to the playback signal, and the headphone type (e.g., brand and model number) used by the user to listen to the audio content. It would also be advantageous to use this information stored in the database(s) during the reproduction of the audio content to provide an equalization signal (“EQ signal”), and to use the equalization signal to calibrate the headphones for an improved and more accurate listening experience.
The present invention provides methods and apparatus having the aforementioned and other advantages. Moreover, the unique combination of components/techniques disclosed herein provides various improvements over previously known structures and techniques.